You only need two output pins to control a stepping motor, step and direction. So with 20 outputs you can in theory have 10 motors.
If you used I2C-based stepper controllers,
Not seen one of those.
Seems like a neat part, though!
It is ready to build intelligent peripheral systems where up to 32 drivers can be connected to one I2C master.
Do you know who stocks them?
said that uno only have 12 outputs but you said that i can get 20 how is that??
each motor need 12v to start and arduino only gives me 5v